Priority and nonpriority service regulating equipment



c. E. GERMANTON 3,297,829

PRIORITY AND NONPRIORITY SERVICE REGULATING EQUIPMENT 9 Sheets-Shaml 1 Jan. 10, 1967 Filed Oct. 25, 1963 Jan. 10, 1967 c. E. GERMANTON 3,297,829

PRIORITY AND NONPRIORITY SERVICE REGULATING EQUIPMENT Filed Oct. 23, 1963 9 Sheets-Sheet E Jan. 10, 1967 c. E. GERMANTON PRIORITY AND NONPRIORITY SERVICE REGULATING EQUIPMENT 9 Sheets-Sheet 5 Filed Oct. 25, 1965 NJSU TQ Naw@ Tok@ @E E gb, Tesla,

RUB wick,

Jan. 10, 1967 c. E. GERMANTON PRIORITY AND NONPRIORITY SERVICE REGULATING EQUIPMENT 9 Sheets-Sheet 4 Filed Oct. 23, 1965 Jan. 10, 1967 c. E. GERMANTON PRIORITY AND NONPRIORITY SERVICE REGULATING EQUIPMENT Filed OC. 25, 1953 9 Sheets-Sheet Jan. 10, 1967 c. E. GERMANTON PRIORITY AND NONPRIORITY SERVICE REGULATING EQUIPMENT Filed OCL. 25, 1963 9 Sheets-Sheet 6 Jan. 10, 1967 c. E. GERMANTON PRIORITY AND NONPRIORITY SERVICE REGULATING EQUIPMENT Filed OCT.. 23, 1963 9 Sheets-Sheet 7 PRIORITY AND NONPRIORITY SERVICE REGULAIING EQUIPMENT Filed oct. 25, 1963 Jan. 10, 1967 c. E. GERMANTON 9 Sheets-Sheet S l Wlwmw IMMWIW MIYQQ IIL milk

hjul

www

@Ummm @ISR Jan. 10, 1967 c. E. GERMANTON PRIORITY AND NONPRIORITY SERVICE REGULATING EQUIPMENT Filed Oct. 23, 1963 9 Sheets-Sheet @6i met Qu d Si NGE @s United States Patent O M 3,297,829 PRIORITY AND NNPRIORITY SERVICE REGULATING EQUIPMENT Charles E. Germanton, Summit, NJ., assignor to Bell Telephone Laboratories, Incorporated, New York,

N.Y., a corporation of New York Filed Oct. 23, 1963, Ser. No. 318,427 21 Claims. (Cl. 179-27) This inventionrelates to switching systems and particularly to switching equipment utilized for regulating the equitable distribution of dierent classes-of-telephone calls to operator positions on a non-priority and priority basis, The present invention further relates to equipment which regulates the ordered sequence in which an idle operator position is made available for serving each of the different classes-of-calls during heavy traffic periods.

In recent years, new switching systems and procedures have been developed for enabling telephone operators to serve several different classes-of-special service calls more efficiently and with less effort. Included among these special service calls are those classified as: person-toperson, dial 0, credit card, charge-to-a-third party, and collect calls. The present invention is concerned with regulating the equitable distribution of such special service calls to operator positions. Accordingly, this invention finds one specific use, by way of example, in a newly developed telephone system of the type disclosed in the R. B. Curtis patent application Serial No. 318,275, tiled concurrently herewith, in which the aforementioned types of special service calls may be received in incoming trunk circuits at a tandem telephone oflce and then be connected to operator positions for service.

In the system set forth in the Curtis disclosure, incoming trunk circuits are segregated into trunk groups in accordance with the nature of the equipment at the originating offices to which the trunk circuits are connected. Each of these groups of trunk circuits is capable of serving some or all of the dial 0, person-to-person, collect, charge-to-a-third party, and credit card classes-of-special service calls served by the tandem system. The trunk circuits of each of these trunk groups are individually associated with one of a number of position link connectors which, under the control of a fewer number of position link controllers, serve to interconnect the calling trunk circuits with the operator positions on both nonpriority and priority bases.

Each of the trunk circuits is arranged for initially requesting connections through the associated position link connector to one of the operator positions on a nonpriority basis at the time it receives an incoming call. After a calling trunk circuit has been connected to a position and the needed assistance has been furnished by an operator, the trunk circuit may be disconnected from the position. Thereafter, if operator assistance again is needed while the call is in progress, the trunk circuit may request connections to the same or another operator position on a priority basis.

The non-priority and priority connection requests received from the trunk circuits are registered in the associated position link connectors. After such requests have been registered and if an operator position is available for serving the classes-of-calls for which the requests are made, the position link connectors compete with one another for engaging an idle one of the position link controllers to control the interconnection of the requesting trunk circuits with the available operator positions.

In accordance with the switching system of the Curtis disclosure, each of the position link controllers assigns an ordered preference to each of the position link connectors and this preference controls the order in which competing position link connectors may engage the controller p 3,297,829 Patented Jan. l0, 1967 ICC to control the interconnection of calling trunk circuits with operator positions. Each of the position link controllers rotates the order of preference after it has served a position link connector for assuring that calling trunk cricuits on one position link connector are not always preferred for connection to operator positions over the calling trunk circuits on the other position link connectors.

While the foregoing preference arrangement promotes the equitable connection of calling trunk circuits to operator positions, it alone is unable to insure that all priority requesting trunk circuits on all of the position link connectors are connected to operator positions before any of the trunk circuits concurrently requesting non-priority connections to the same positions. This inability results from the fact that a position link connector having only a registered non-priority request is at certain times more preferred for engaging a position link controller than another position link connector having a registered priority request. As a consequence, with such an arrangement alone, non-priority requesting trunk circuits would at times be connected to operator positions before priority requesting trunk circuits.

In view of the foregoing, it is apparent that additional equipment is required for regulating the ordered sequence in which priority and non-priority requesting trunk circuits on the different position link connectors are interconnected with operator positions and, more specifically, for regulating the sequence in such a manner that a plurality of position link connectors are enabled to connect priority requesting trunk circuits to operator positions before any non-priority requesting trunk circuits.

A further consideration for the foregoing system is that it is important, from a traffic service standpoint, for operator positions to be able to serve, on an equitable basis, each of the classes-of-calls which they may have been adapted, or preconditioned, to serve. The Curtis tels-phone system is adequately equipped for enabling operator positions to receive the appropriate classes-ofcalls one at a time and to serve all such calls on an equitable basis during light traffic periods. However, in order to serve such calls on an equitable basis during heavy traffic periods, it is imperative that some additional means of regulation be employed in the system for regulating the ordered sequence in which the operator positions are made available for serving the different classes-of-calls which may be awaiting priority and non-priority connections to the positions. Otherwise, certain problems arise in the system which make it extremely difficult for operators to serve the different classes-of-calls in the approximate order in which they are received in the system. For instance, when al1 operator positions are busy and operators become idle one by one after serving a call, an idle operators position would immediately become available for receiving any one of the different classes-of-calls which it is` preconditioned to serve. As a consequence, the preference arrangements incorporated into the position link connector and controller circuits would not recognize which classes-of-calls were received earliest and usually would be unable to connect calls to the operator position in the order in which they were received in the system during the heavy traflic period. Thus, without additional equipment, certain classes-of-calls may be forced to wait while later received classes-of-calls are served repeatedly.

In view of the foregoing, it is an object of my invention to provide switching equipment for regulating the equitable distribution of a number of different classes-of-telephone calls to operator positions on non-priority and priority bases.

Another object is to provide switching equipment for regulating the ordered sequence in which priority and non-priority requesting trunk circuits on different position link connectors are interconnected with operator positions to insure that priority requesting trunk circuits are connected to the positions before non-priority requesting trunk circuits.

It is a further object to provide switching equipment for regulating the ordered sequence in which operator positions are made available to serve different classes-ofcalls during heavy tratiic conditions in order that the calls may be served on an equitable basis in the approximate order in which they are received in the system.

Yet another object is to provide switching equipment for regulating the ordered sequence in which operator positions are made available during heavy traic periods to serve diiferent classes-of-calls awaiting priority and non-priority connections to the positions which are selectively preconditioned for serving some or all of the ditferent classes-Of-calls.

These and other objects are attained in accordance with an exemplary embodiment of my invention wherein switching equipment is provided for use in a telephone system, as set forth in the Curtis disclosure, for regulating the call traiic to operator positions and, particularly, for regulating the traic in such a manner as to enable calls in all priority requesting trunk circuits to be connected through position link connectors to the available positions before non-priority requesting trunk circuits.

In accordance with the present invention, a traflic regulator circuit ascertains the availability of the operator positions to serve each of the diiferent classes-of-calls and supplies appropriate position available and positions busy signals to a plurality of position link connectors for controlling the interconnections of calling trunk circuits with operator positions on both non-priority and priority bases. Specifically, the tratiic regulator is activated when a trunk circuit has registered a priority request in one of the position link connectors for supplying position available signals to that connector in accordance with the actual availability of the operator positions to serve the different classes-of-calls. At the same time, the regulator supplies positions busy signals to all of the other position link connectors of the system which do not have registered priority requests and these busy signals signify that all positions are busy to those connectors. As a consequence, only the position link connector receiving the position available signals is enabled to engage a position link controller for controlling the interconnection'of the priority requesting trunk circuit with an available position. In contrast, the position link connectors receiving the positions busy signals are blocked from engaging a position link controller until after the priority requesting trunk circuit has been connected to an operator position.

The traffic regulator further includes apparatus for regulating the order in which calls requesting non-priority and priority connections are served during heavy traic periods when operator positions become idle one by one after serving a call. Instead of making the idle position immediately available for serving all classes-of-calls which it is conditioned to serve, this apparatus immediately makes it available for serving certain of those classes-ofcalls and then, after a timed delay interval, makes it available for serving all of the other classes-of-calls which it is conditioned to serve. Among the classes-of-calls, for which the idle position is immediately made available, are: a call for which a trunk circuit is requesting priority service and a call for which a trunk circuit has been requesting non-priority service longer than certain other of-calls served by the system and it is operative under the control of the corresponding class relay for supplying positions busy and position available signals to all of the associated position link connectors.

During heavy traiiic periods when all operator positions are busy, all of the positions busy relays are operated to supply positions busy signals to all of the position link connectors for temporarily blocking them from engaging the position link controllers. At the same time, certain of the positions busy relays are made slowreleasing by shunting their secondary windings by a low impedance. These slow-releasing relays correspond to the classes-of-calls which presently do not require priority service or which have not been awaiting non-priority service longer than certain other classes-of-calls. In contradistinction, the positions busy relays corresponding to the classes-of-calls which have been waiting longer than certain other classes-of-calls are concurrently fast releasing devices.

The traic regulator comprises a priority circuit which identifies when any one of the position link connectors has registered a priority request and this circuit thereupon is activated for opening the shunting paths around the secondary windings of all of the positions busy relays to make them fast releasing. This mode of operation insures tha-t when an operator position becomes idle, position available signals are quickly supplied to the position link connector having the priority request for rapidly effecting the connection of the priority requesting trunk circuit to the idle operator position.

The traic regulator also employs a call-waiting control circuit for ascertaining the approximate order in which the dilferent classes-of-calls are received in the system and for appropriately controlling the fast and slow release characteristics of the positions busy relays to insure that longer waiting classes-of-calls may be served before the relatively shorter waiting classes-of-calls.

At the time that an operator position becomes idle during the heavy traflic period, the faster releasing positions busy relays are enabled to release under the control of the corresponding class relays for supplying position available signals to all position link connectors for the corresponding classes-of-calls before the slower releasing positions busy relays are able to release for supplying position available signals for their corresponding classof-calls. Accordingly, the position link connectors are enabled to compete with one another for engaging an idle position link controller for connecting a priority requesting trunk circuit to available position before any non-priority requesting trunk circuit, and for connecting a longer waiting non-priority requesting trunk circuit to the position before a shorter waiting non-priority requesting trunk circuit when no trunk circuit is requesting priority connections during the heavy traic period.

It is a feature of my invention that switching equipment regulates the connection of call traic requesting both non-priority and priority connections to operator positions by supplying position available and positions busy signals to a number of connector circuits for enabling those circuits to interconnect all calls requesting priority service with available operator positions before any call requesting non-priority connections.

Another feature is that switching equipment is provided for regulating the equitable connection of a number of different classes-of-calls to operator positions or nonpriority and priority bases by supplying position available signals to the connector circuits having a priority connection request from a calling circuit and positions busy signals to other connector circuits having a nonpriority connection request from a calling circuit.

A further feature is the provision of switching equipment for regulating the ordered sequence in which an operator position is made available for serving a plurality of different classes-of-calls during heavy trafiic periods and, particularly, for regulating the sequence so that the longer waiting classesofcalls are served before shorter waiting classes-of-calls during heavy traiiic periods.

Yet another feature is that trafc regulating equipment includes an individual class relay for each one of the classes-of-calls served by a telephone system for indicating when at least one operator position is available to serve that class-of-call, and an individual positions busy relay which is controlled by one of the class relays for supplying position available and positions busy signals to connector circuits for enabling the longer waiting classes-of-calls to be connected to opera-tor positions befo're the shorter waiting classes-of-calls during heavy traffic periods.

Still another feature is that the positions busy .relays be selectively controllable by a call-waiting circuit in the trailic regulating equipment to have either a fast or a slow release characteristic during heavy traic periods, that each of the fast release positions busy relays correspond to a class-of-call which has been waiting for connections to an operator position longer than certain other classes-of-calls, that the slow release positions busy relays correspond to the shorter waiting classes-of-calls, and that, when an operator position becomes idle, the fast release relays immediately release for supplying position available signals to the connector circuits for effecting the connection of the longer waiting classes-ofcalls to the idle operator position in preference to the shorter waiting classes-of-calls.

It is another feature of my invention that the positions busy relays be controllable by a priority circuit in the traic regulating equipment to have the fast release characteristic whenever a call is requesting priority connections to an operator position and thereby to insure that, when an operator position becomes idle after an all positions `busy condition, position available7 signals for all classes-of-calls served by that position are quickly supplied to the connector circuits for rapidly connecting the priority requesting call to the idle position.

A complete understanding of the foregoing and other advantages and features of my invention may be gained from a consideration of the following description, together with the accompanying drawing, in which:

FIGS. 1 and 2 are block diagrams depicting the equipment of the illustrative embodiment and comprise a group of ten position link connectors and a CAMA position link employed in a tandem telephone system for connecting 500 incoming trunk circuits and 40 senders to 66 operator positions through position control circuits and position circuits under the control of position link controllers and a trafc regulator;

FIGS. 3-9, inclusive, show in block and schematic form the essential circuit details of ten position link connectors, three position link controllers, a CAMA position link, a key control position control circuit, position control circuits, and the tratiic regulator; .and

FIG. 10 depicts the position in which FIGS. 1-9 should be placed to show the cooperation between the equipment units.

It is noted that FIGS. 3-9 employ a type of schematic notation referred to as detached-contact in which an X crossing a line represents a normally opened contact of a relay and a bar crossing a line represents a normally closed contact of relay or key; normally referring to the unoperated condition of a relay or key. The principles of this type of notation are described in an article entitled An Improved Detached-Contact-Type Schematic Circuit Drawing, by F. T. Meyer in the September 1955 publicati-on of the American Institute of Electrical Engineers (AIEE) Transactions, Communications and Electronics, vol. 74, pp. 505-513.

Each relay contact is designated in the drawing in a manner which indicates the relay of which it is a part and as well uniquely identities it with respect to other contacts of the relay. For example, referring to relay contact CWO1 of FIG. 3, it is noted that the CWO 6 part of the designation indicates that it is controlled by relay CW() of FIG. 3 and the -1 uniquely identities it with respect to another contact CWO-2 of relay CWil, the latter contact being also shown on FIG. 3.

The equipment of the present invention may be advantageously incorporated in an automatic tandem telephone system wherein common control circuits are employed to control the establishment of calls through a switching network. One such system is disclosed in aforementioned R. B. Curtis application (hereinafter referred to as the Curtis disclosure). It is to be understood, however, that the present invention is not limited to use with a telephone system of this type, but that it may also 4be utilized with other types of switching system, such as local and toll systems.

The equipment illustrative of the principles of the present invention has been embodies in a tandem system of the type disclosed in the Curtis disclosure. It is particularly concerned with the apparatus in the position link connectors PLO-PL9, position link controllers LCtl-LCZ, CAMA position link and controller CPL and CLC, position control circuits PCC1-PCC66, and the key control position control circuit KCP shown in heavy lines on FIGS. l and 2. The other equipment units are neither shown nor described in detail herein except where necessary for a complete understanding of the present invention. The cited Curtis disclosure together with I. Baumfalk-T. P. McGuinness-R. C. Nance patent application Ser. No. 318,407, N. L. Laefer patent application Ser. No. 318,355, and A. H. Scheinman patent application Ser. No. 318,360, tiled concurrently herewith may be consulted for a cornplete understanding of the construction and operation of the units not covered in detail herein. The CAMA position link and controller CPL and CLC of FIGS. l and 7 form a part of the tandem system in the Curtis disclosure, but it is disclosed in more extensive detail in the R. N. Breed et al. Patent 2,848,543, granted Aug. 19. 1958.

GENERAL DESCRIPTION The general organization of the principal equipment units of the illustrative embodiment of my invention will now be described with reference to FIGS. l and 2. The crossbar tandem system as set forth in the aforementioned Curtis disclosure is designed to serve several different classes-of-calls, such as person-to-person calls and other special service calls, such as dial 0, coin, charge-to-athird party, credit card and collect calls, as well as CAMA (Centralized Automatic Message Accounting) calls. These types of calls are extended t-o the tandem system from an originating oflice via incoming trunks, such as the special service trunks TKOilTK94 and the CAMA trunk CT. Each of these trunks is illustrative of the numerous trunks provided for a fully equipped tandem system for serving each of the diierent classes-'of-calls. The trunks TK00-TK94 and CT are terminated individually in the incoming trunk circuits TCtO-TC94 and CTC, respectively.

Each of the trunk circuits TC00-TC94 and CTC has two principal appearances in the switching network of the tandem system. One appearance is on the trunk link frame TLF and is used for establishing the talking connections for the calling and called stations through the office link frame OLF and outgoing trunk circuit OTC in almanner as set forth in the cited Curtis disclosure and Breed et al. patent.

A second appearance is on the sender link SL and is used for passing information to and from the common control circuits, such as the senders SBO-S39 and marker M, of the system. Trunk circuits TC00-TC94 each have another appearance on the operator position link connector circuit and it is used for selectively connecting the trunk circuit to operator positions on non-priority and priority bases.

In the illustrative embodiment of my invention, the dial O and other special service trunk circuits, such as circuits TC-TC94, are segregated into trunk groups according to the class-of-calls which they serve. There are a maximum of ten trunk groups on each of the position link connectors PLO-PL9, namely, trunk groups 0-9. Each such group comprises only trunk circuits that serve the same class-of-call. There are ve trunk circuits in each trunk group on the position links PLO-PL9. Thus, a maximum of ten different class-of-service trunk groups can be served by each of the position link connectors PLO-PL9. However, in this illustrative embodiment, only six different class-of-service trunk groups are shown. This arrangement facilitates the control over the circuit operations involved in interconnecting the trunk circuits with operator positions and permits the circuits in each class-of-service group to be served on an equitable basis under the control of the trac regulator TR.

Each designation of the trunk circuits TC00-TC94 includes a numbeicomprising a digit indicating the trunk group into which it has been placed and a digit which uniquely identifies it within that group. To illustrate, the designation of trunk circuit TC00 includes the number 00 which compises the first digit 0 to indicate the trunk group 0 and the last digit O uniquely to identify the trunk circuit relative to the other four trunk circuits in the same group.

For requesting connections to the operator positions on non-priority and priority bases, each of the dial O and special service trunk circuits, such as circuits TC00-TC94, is equipped with non-priority and priority start leads NPSO-NPS94 and PSO-P594, respectively. The trunk circuits may selectively request connections to the operator positions either on a non-priority or a priority basis by applying a service request signal to the appropriate non-priority or priority start lead.

Each of trunk circuits on the position link connectors PLO-PL9 is arranged for initially requesting connections to one of the operator positions OPI-0F66 on a nonpriority basis at the time that it receives an incoming call. After this call has been served by an operator, the operator position may be disconnected from the calling trunk circuit. Thereafter, the calling trunk may selectively request connections to the same or another operator position on a priority basis when assistance again is required on the call.

It may be seen in FIGS. 1 and '2 that a position link connector and a position link controller circuit, such as circuits PLt) and LCO, together provide the facilities for interconnecting the dial O and special service trunk circuits, such as circuits TC00-TC94, with the operator positions OP1-OP66 via position control circuits and position circuits PCC1-PCC66 and PC1-PC66. The position link connectors PLO-PL9 comprise the actual interconnecting means and each of the position link controllers LCO-LC2, las its name implies, controls the operations of the position link connectors PLO-PL9 in such a fashion that all of the calling trunk circuits are interc-onnected with operator positions on :an equitable basis.

Each of the position links PLO-PL9 includes individual non-priority and priority register-start circuits, such as circuits NPRSO-NPRS9 and PRSO-PRS9 of FIGS. l and 2, for each of the class-of-service trunk groups. These register-start circuits register non-priority and priority service requests received from the associated fifty trunk circuits and apply appropriate non-priority and priority start signals to both the traffic regulator TR and the associated position link controllers LCtl-LC2. N-on-priority request-s are received by the position link connectors PLO-PL9 from the dial O and special service trunk circuits over the leads NPS- and are applied to the nonpriority register-start circuits, such as circuits NPRSO- NPRS9, through individual class-of-service gate circuits, such as circuits CGO-CG9. Each of these gate circuits is controlled by the traflic regulator TR in order to insure that the dial O and special service calls received by the incoming trunk circuits are served in the approximate order in which they are presented for service.

Priority service requests from dial O and special service trunk circuits are received by the position link connectors PLO-PL9 over the priority start leads PS- and are registered in the priority register-start circuits, such as circuits PRSO-PRS9, independently of the gating systemempfloyed for the registration of non-priority requests. As a consequence, the priority register-start circuits are effective to activate the traic regulator TR and one of the position link controllers LCO-LC2 for allowing the priority requesting trunk circuits to be interconnected with operator positions before any of the non-priority requesting trunk circuits.

As is indicated in FIGS. 1 and 2, each of the position link connectors PLO-PL9 in the -presently disclosed embodiment has a maximum of fifty trunk circuits connected Ito its input and 198 posit-ion loops connected to its output. Illustrative of the latter arrangement is the connection of the trunk circuits TC00-TC94 (fty trunk circuits) to the input of the switching network SN of the position link connector PL() and the position loops L0-L197 to the output of network SN. Each of the position link connectors PLO-PL9 employs a switching network SN for connecting trunk circuit information 4and control leads, such as the leads of the cables ICCO and ICC94 of FIG. 2, to the position loops L0-L197.

Turning now to the CAMA equipment features, it may be noted that incoming CAMA trunk circuits, such as circuit CTC of FIG. 1, are connectable through the sender link SL to the senders SIW-S39 in a manner as disclosed in the cited Breed et al. patent. Senders S00-S39 are divided into four groups of ten e-ach, namely, sender groups 0-3. These groups -of senders are connected over the information and control leads of the cables CICO- CIC39 to the switching network CSN of the CAMA position link CPL by which the senders S00-S39 are enabled to connect with any one of the 66 operator positions over the CAMA position loops CL1-CL66 under the control of a CAMA position link controller, such as controller CLC.

Senders S00-S39 are provided with means for requesting -only routine, or non-priority, connections through the switching network CSN to the operator positions OP1- OP66. The routine connection requests are received by the position link CPL from the senders SUO-S39 over the sender start leads SS00-5539 and are applied to the register-start circuits RSO-KS3 through the individual gate circuits GCO-GC3. The latter circuits are controlled by the traffic regulator TR to insure that the CAMA calls served by the senders S00-S39 are connected to the positions OP1-OP66 in the approximate order in which they are presented for service.

In the following description, the position link connectors PLO-PL9 and the CAMA position link CPL may be referred to simply as a position link or as a link. Accordingly, this terminology is used extensively throughout the remainder of the specification.

The position link connectors, such as links PLO-PL9, are arranged together into link groups, each of which comprises ten position link connectors. An arrangement of the position link connectors forming one such link group and the association of those position link connectors with incoming trunk circuits, position link controllers, operat-or positions, a traflic regulator and other control circuits is illustrated in FIGS. 1 and 2. Three position link controllers are provided for each link group to control the ten position link connectors.

Sixty-six operator positions are connected to the ten position links PLO-PL9 and the CAMA position link CPL via individual position circuits and position control circuits as well as the aforementioned position loops L0- L197 and CL1-CL66. Each of the position control circuits, such as circuit PCCl, of the position units PUI- PU66 is individually associated with three loops, such as Iloops Lil-L2, extending to the position links PLi-PL9, and one of the CAMA loops, such as loop CL1, extending to the position link CPL. Thus, the position links PL- PL9 and CPL serve to interconnect -any one of 500 incoming trunk circuits and 40 senders with any one of 66 position control circuits rvia 264 position loops.

Each lof the 66 operator positions is provided with a Iposition unit, such as unit PUI of FIG. l, which comprises a lposition control circuit and a position circuit. These circuits, together with the equipment at the operator position, provide four loop circuits whereby an operator may serve calls. Each of the position control circuits, for example, circuit PCCl of FIG. .2, includes facilities for automatically conditioning each of the associated loops for connecting calls one by one through the position circuit to the operator position. The control circuit also comprises apparatus for enabling an operator to connect her telephone to any calling loop associated with her position and to place a hold condition on any calling loop while she serves a call on another loop.

A key control position control circuit KCP of FIG. 2 is associated with the position control circuits PCCl- PCC66 for selectively preconditioning the operator positions OPT-F66 for serving one or more of the six different classes-of-calls receivable from the trunk circuits TCM-TCM. The individual position control circuits PCCl-PCC66 inform the control circuit KCP whether the associated operator i-s available to serve each of the different classes-of-calls and circuit KCP, in turn, passes that information to the traffic regulator TR for enabling it to regulate the ordered sequence in which each of the different classes-of-calls is distributed to the operator positions OPT-0F66.

An operator can actively serve only one call `at a time in this exemplary embodiment even though four loops7 such as loops Lil-LZ and CLll, are provided for each position. In addition, when an operator is actively serving a call on one loop, the position link appearances of the remaining three loops will .appear ybusy and no calls will be offered to these loops at that time. Four loopA circuits are provided for each position because, on some of the calls, the calling loop may be utilized for the entire duration of the call. Accordingly, it' only one loop circuit was provided and it Was utilized for serving such a call, the operator would ibe idle and would have no functions to perform for the duration of the call after she had completed the rservices required of her in connection with the establishment of that call. By providing four loops, a call can be offered to any idle loop while another loop in the same group is being utilized on another call for which the operator has completed the active servicing thereof. To facilitate the serving of such a call on an idle, or unused, loop, the position control circuit changes the busy condition on the position link appearances of the unused loop to an idle condition after the operator completes the active servicing of a call on another loop. Thus, the serving of the 264 position loops by the 66 operator positions enables a plurality of incoming calls to be extended to and served by a plurality of operators with minimum delay.

The traic regulator TR of FIG. 2 regulates the distribution of calls to the operator positions OPI-0F66 from all trunk circuits served by the position links PL- PL9 and from the 40 senders associated with the position link CPL. The regulator TR controls the distribution by ascertaining the service demands Iby the various trunk circuits and senders, as well as, the availability of operator positions to serve these demands. It accomplishes the regulation by controlling the gate circuits CGOCG9 and CGO-CG3 of FIG. l and by controlling the position availability signals which it supplie-s to the position busy circuits PBCO-PBC9 and GBAC-GBGC of the position links PLU-PLQ and CPL.

The regulator TR controls the gate -circuits CGO-CG9 and GCO-GCS to admit service requests concurrently rel@ ceived from groups of calling trunk circuits and senders into the associated register-start circuits NPRSO-NPRS9 and RSORS3 in order that the trunk circuits and senders may be connected on a non-priority basis to available ones of the operator positions OPI-0F66 on an equitable basis. After these requests have been admitted and registered, the regulator TR closes the gates in the position links to lock out from those links all other senders and trunk circuits which are in the same class-of-service trunk and sender groups as the circuits having already registered requests, and which may subsequently request connections on a non-priority basis to the operator positions OPI-0F66. This insures that incoming calls requesting the same class-of-service are served in the approximate order in which they are received at the tandem oflice. After the closure of the latter class-of-service gates, the regulator allows non-priority service requests from trunk circuits in other class-of-service groups to be admitted and registered in the position links and these latter trunk circuits may compete for connections to the operator positions with the other trunk circuits and senders which have previously registered non-priority service requests.

Regulator TR also cooperates with all of the associated position links PLO-PL9 and CPL, as well as the link controllers LCtl-LCZ to provide for the connection of trunk circuits to the operator positions OPl-OPoe on a priority basis. When a trunk circuit requests priority service, the regulator is activated to supply positions busy signals to the positions 'busy circuits PBC-PBC9 and GBAC- GBGC for making all of the operator positions OPT- OP65 appear busy to all of the position links CPL and PLQ-PL@ which are not associated with a trunk circuit requesting priority service, and while at the same time, allowing the available positions to appear idle to each of the position links associated with a priority requesting trunk circuit. As `a result, each priority requesting trunk is connected through the switching network, such as network SN, of the position link to an available position before any trunk circuit or sender requesting non-priority service.

Regulator TR also provides for the eflicient use of the three position link controllers LC-LCZ by the ten position links PLQ-PLQ. The efficiency is achieved because the regulator TR, after it has checked the availability of the operator positions to serve the trunk circuits requesting service, sends position available signals to all ten of the position links PLO-PL9 and, accordingly, allows each of these links to seize one of the controllers LC@- LC2 only if an operator is available to serve a call on a trunk circuit having a request registered in that link.

Further in accordance with the present invention, the trac regulator TR regulates the ordered sequence in which the operator positions OPT-0F66 are made available to serve the six different classes-of-calls served by the position links PLO-PLQ and the CAMA calls served by the CAMA position link CPL, during heavy trai-lic periods when the operator positions become idle one by one. It accomplishes this regulation by initially admittingr into its call-waiting and master gate control circuit groups of trunk circuits and senders which are concurrently requesting connections to the positions OPI-0F66. This control circuit then effects the closing of the appropriate ones of the control gates CCO-CG@ and GCO-GCS on the position links PLO-PL9 and CPL for blocking the registration of subsequently received non-priority requests.

When all of the positions are busy, unoccupied, or otherwise unavailable during a heavy traiiic period, the traffic regulator TR supplies positions busy signals for activating all of the positions busy circuits PBCil-PBC9 on each of the position links PLil-PLQ and all of the positions group busy circuits GBAC-GBGC on the CAMA position link CPL to inform these links of the non-availability -of the positions OPT-0F66. A positions busy circuit is provided on each of the position links PLO-PL9 for each of the six different classes-of-calls served by those links. A positions group busy circuit is provided on the CAMA position link CPL for each of the seven diiferent groups into which the operator positions CP1-0F66 are segregated.

As the positions OPI-F66 become idle one by one during the heavy traic period, the regnilator TR signals the position links PLO-PL9 before the CAMA position link CPL that a position is available. In certain instances, the now idle position will have been preconditioned for serving a number of the classes-of-calls presently on the trunk circuits and senders admitted into the call-waiting and master gate control circuit, as well as the other classes-of-calls on trunk circuits which have not been so admitted and which are presently requesting nonpriority connections to the positions CP1-0F66. However, the regulator TR will insure that the idle operator position is made available for connection to one of the admitted trunk circuits or one of the other trunk circuits which is requesting priority connections. In doing so, the regulator TR will prefer connection to the idle operator position those trunk circuits which have been admitted into the master gate control circuit and will handicap the trunk circuits as well as senders which have not been so admitted unless the trunk circuits are requesting priority connections to the operator positions. The regulator accomplishes this pre-ference and handicapping of both trunk circuits in the different classes-of-service and senders by supplying position available signals to links PLO-PL9 for deactivating the positions busy circuits PBCO-PBC9 which correspond to the admitted and priority requesting groups of trunk circuits before supplying such signals for deactivating the positions busy and group busy circuits corresponding to the other groups of trunk circuits and senders which have not been admitted and which the idle operator is capable of serving. By supplying the position available signals in this order, each of the position links PL-PL9 is enabled to seize one of the link controllers LCO-LC2 for effecting the interconnection of the admitted and priority requesting trunk circuits to the positions OP1-OP66 before the non-adrmitted trunk circuits and senders.

After all of the admitted and priority requesting groups of trunk circuits on the links PLO-PL9 have been connected to operator positions and positions are yet becoming idle one Yby one, the regulator TR prefers the admitted groups of senders for connection to the idle operator position and handicaps the groups of trunk circuits on links PLO-PL9 which have not been admitted and are not requesting priority connections to the positions. This regulation is accomplished by supplying position available signals to the CAMA link CPL for deactivating the group busy circuits GBAC-GBGC before supplying such signals for deactivating the positions busy circuits PBCO-PBC9 on the links PLO-PL9.

DETAILED DESCRIPTION Referring now to FIGS. 3-9, a detailed description will be presented of the circuit operations involved in providing for the regulation of the connection of incoming special service and CAMA calls to the operator positions OP1-OP66. This description is directed only to those circuit details necessary for a clear understanding of the present invention. Other circuit details necessary to integrate the present invention into an operating tandem system are set forth in the cited Curtis disclosure. Accordingly, FIGS. 3-9 show only the structural details of one traffic regulator TR and the control leads over which that regulator is interconnected with apparatus of the position links PLO-PL9, position link controllers LC()- LCZ, CAMA position link CPL, position control circuits PCC1-PCC66 and' the key control position control circuit KCP.

Call-waiting and gate c0ntr0l.-In FIG. 3, it may be noted that there are tive call-waiting relays CWtl-CWS in the traic regulator TR. Each of these relays is individually identified with one of the six different class-ofservice trunk groups on each of the position links PLO- PL9 and is utilized for indicating when a call is waiting to be served in that trunk group. It may be emphasized that there are only six different classes-of-service in this illustrative embodiment and that each of the position links PLO-PL9 serves ten trunk groups. Therefore, certain of the trunk groups on the same position link must be assigned to the same class-of-service and ybe identified with the same one of the relays CWO-CWS.

Referring to the left side of FIG. 3, the terminals T0- T9 are associated with the ten different trunk groups on the position link PLO. One of the two make contacts ST- and ST-P- intermediate each of the T- terminals and ground is closed if a trunk circuit in the associated group is currently requesting either non-priority or priority connections to one of the operator positions OP1- OP66 (FIGS. l and 2) for a class-of-service call represented by t-he T- terminal. These contacts are controlled by the non-priority and priority start relays ST- and ST- P, respectively, (not shown in the present drawing but shown in FIGS. lO7A-l07C of the Curtis disclosure) which are included in the non-priority and priority register-start circuits NPRSO-NPRS9 and PRSO-PRS9 depicted in FIGS. 1 and 2. Thus, for example, ground will be applied through contact STO-1 to the terminal T0 only in the event that a trunk circuit in trunk group 0 is requesting non-priority connections to an operator position. Similarly, ground will be applied through contact STOP-1 only if a trunk circuit in trunk group 0 is requesting priority connections to an operator position.

The cross-connection between the terminals T0-T9 and the terminals TAG-TAS of FIG. 3 classifies each of the ten groups of trunk circuits of position link PLO to one of the six different classes-of-service. In the exemplary embodiment, the trunk circuit TC00 of FIG. l is of the dial O class-of-service and is in trunk group 0 of position link PLO. Consequently, terminal T0 is connected to terminal TAO there-by indi-eating that all calls served by trunk group (l of position link PLO will be of the dial O type. There are ten terminals T 0-T9 and only six terminals TAO-TA5 and therefore certain of these TA- terminals must be connected to more than one of the T- terminals. Accordingly, a plurality of the trunk groups on position link PLO must *be assigned to serve the same class-of-service calls.

For the purpose of illustration, it may be assumed that the dial O trunk circuit TC00 of FIG. 1 has presented a service request over either the non-priority or priority start lead NPSO or PSO during a lull in traffic when no other trunk circuit served by the same link group is currently requesting connections to an operator position which is presently available to serve a dial O call. The non-priority request is applied through the control gate CGO of FIG. l and is registered in the associated nonpriority register-start circuit NPRSO. On other hand, the priority request is applied directly to the priority registerstart circuit PRSO of FIG. 1. After the registration of the non-priority or priority request, either the relay STO or STOP (not shown in the present drawing but shown in FIGS. 107A-l07C of the Curtis disclosure) is operated as set forth in the Curtis disclosure and causes the operation of relay OG of FIG. 3. The latter relay operates over the path from the negative potential P1 through its winding, diode D0, contact CWO-1, lead CWLO, terminals TAO and T0 and contact STO-1 or STOP-1 to ground.

Before describing the circuit operations that follow the operation of relay OG, it is `advisable at this point to explain certain of the priority service features of the traffic regulator TR. Referring to FIG. 3, it may be seen that there are ten priority frame relays PFO-PF9 in the regulator TR. Each of these relays is connected over one of the leads PFLO-PFL9 to one of the position links y-PLtl-PL9, and is operated whenever a priority request has been registered in that position link. F'or example, whenever a priority request nas been registered in one of the priority register-start circuits PRStl-PRSSl of link PLI), the corresponding one of the STtlP-ST9P relays (not shown) of that link is operated to complete a circuit for operating the relay PF@ of FIG. 3. This circuit is from the negative potential P2 through the PF1) relay winding, lead PFLtI, contact LCC-1, and one of the contacts STP-Z through ST9P-2 to ground. When one of the relays PFtl-PF9 operates, it in turn operates certain of the non-priority relays NPG-NP9 of FIG. 9, as hereinafter described, for causing all positions busy signals to be supplied t-o all of the position links PLtl-PL9 except that link having the registered priority request. The manner in which the NPG-NP9 relays are operated and the busy signals are supplied to the various position links is deferred for explanation in the following section entitled Position Availability Signals to Position Links PLtl-PLQ.

When one of the PFtl-PF9 relays is operated, it causes the operation of the priority relay PR of FIG. 8 over the path from the negative potential P17 through the PR relay winding and a make contact, such as contact PFtl-9, of the operated one of the PFtl-PFSV relays to ground. In operating, relay PR activates all of the positions group relays GBA-GBG of FIG. 8 over the parallel paths from ground through the GBA-GBG relay windings and the make contacts, such as contacts PII-3 and PR-, of relay PR to the negative potential P16. The operations of the GBA-GBG relays, in turn, cause the operations of the group busy relays AGBA-AGBG in the CAMA position link CPL of FIG. 7. By operating relays AGBA-AGBG, the trallic regulator TR informs link CPL that the operator positions OPI-F66 of FIG. 1 are not presently available for serving CAMA calls. Accordingly, link CPL is unable to connect a CAMA trunk circuit to an idle one of the positions OPI-0F66 while, on the other hand, the idle positions are made available for connection to the priority requesting trunk circuits on the links PL@- PL9 as later explained. Relays AGBA-AGBG operate over the parallel paths in FIG. 7 from ground through their windings, leads GBLA-GBLG and make contacts of the relays GBA-GBG to the negative potential P6.

In addition, when one of the relays PFS-PF@ is operated, it causes the negative potential PIS of FIG. 8 to be connected through one of its make contacts, such as contact PFG-8, to lead CWPL for operating the callwaiting priority service -relay CWP in each of the link controllers LCtl-LCZ of FIG. 1 when these controllers are engaged in connecting non-priority requesting trunk circuits on links PLQ-PLQ with the position OPI-0F66 at the time the priority request is registered in one of the links PLtl-PL9. The operation of relay CWP in any of the controllers LCti-LCZ informs that controller to finish connecting the non-priority requesting trunk circuit with one of the positions OPI-OPM and then to initiate a series of circuit actions, as set forth in the cited Laefer disclosure, wh-ereby cach priority requesting trunk circuit is thereafter connected to one of the positions OPI- OP66 before any non-priority requesting trunk circuit.

Continuing now with the description of the circuit operations that follow the operation of relay OG, it is noted that after relay GG operates, it causes the operati-on of the call-waiting relay CW of FIG. 3 over the path from the potential P1 through its winding and contact OG-l to ground. The oper-ation of relay CW operates the master gate relay MGT of FIG. 3 over the path from potential P1 through its winding, contacts CWS-2, CW4- through CWl- (not shown), CWtl-Z, CW-l and OG-2 to ground. Upon operating, relay MGT locks through contacts MGT-1, CW-l and OG-Z to ground.

The operation of relay MGT admits the dial O call into the control of the master gate relay circuit and also operates the call-waiting relay CW@ which is associated with the dial O class-of-service. Relay CW() operates in the path from potential P1 through its winding and contact MGT-2 to the ground supplied on lead LWL() via terminals TAO and To and contact STU-1 or STUP-Il of link PLtl. When operated, relay CW() locks through its contact CWtD-S to the ground on lead CWLtl. At the same time, relay CWtl provides a supplementary operate path for relay CW through contact CWO-4 to ground. Relay CW@ also opens contact CWtl-l to release relay OG. Upon releasing, relay OG opens contact OG-Z to release relay MGT. Thus, the traic regulator TR has recognized that a dial O class-of-service trunk circuit is requesting connections to one o-f the operator positions OPI-0F66 of FIGS. 1 and 2.

After relay MGT releases, it may not be reoperated until after contact CWtl-Z is reclosed upon the release of relay CWtl. The latter relay is released following the connection of the truuk circuit TCtltl to one of the operator positions OPI-0F66 of FIGS. 1 and 2 as later explained. Thus, trunk circuits in class-of-service trunk groups other than the dial O groups may register nonpriority connection requests in the position links PLtl-PL9 as described in the Curtis disclosure and cause the grounding of the leads CWLl-CWLS of FIG. 3 after relay MGT has been released.

The grounding of any one of the leads CWLl-CWLS will cause the reoperation of relay OG of FIG. 3, for example, over the path from lead CWLS through contact CWS-ll, diode D5 and the OG relay winding to potential PI. However, in operating, relay OG cannot reoperate relay MGT 'because contact CWtl-Z is opened. Accordingly, none of the relays CWI-CWS may be operated until after relay MGT is reoperated because make contacts of relay MGT, such as contact MGT-3, are serially connected in the operate circuit of these relays and are presently opened to prevent a ground on the CWLI- CWLE leads from completing the operate circuit for the relays CWI-CWS. Hence, non-priority requests of other trunk circuits of trunk groups other than the dial O groups will not be blocked from being registered in their associated non-priority register-start circuits of the position links PLil-PL9 during the period while circuit TC is being connected to one of the operator positions OPI- OP66. These other non-priority requesting trunk circuits may then be connected to the operator positions OPI- OP66 at the same time as circuit TCttl in ia manner as explained in the Curtis disclosure if there are enough of the operator positions available to serve the calls thereon.

Following the operation of relay CWtl, all control gate circuits, such as circuit CG@ of FIG. 1, of the position links PLQ-PLQ which are associated with the dial O class-of-service trunk groups are closed, as hereinafter explained, to 'block the registration of subsequent nonpriority requests in the non-priority register-start circuits of links PLtl-PL9. This insures that dial O trunk circuits are connected to operator positions OPI-0F66 in the approximate order in which they receive dial O calls.

Before describing the circuit actions that follow as a result of the operation of relay CWi), it is advisable to present a few remarks with regard to the circuitry of FIG. 4. It may be seen in FIG. 4 that there are ten G- relays, Gti-G9, in the position link PLtl. One of these relays is included in each of the control gate circuits CGll-CG9 of FIG. l. These relays are operative under the control of the call-waiting relays CWG-CWS to block the registration of requests in the non-priority registerstar-t circuits, such as circuits NPRSO-NPRS9, of the position links PLO-PL9. Referring specifically to the position link PL() by way of example, it Imay be noted that the winding of each of the relays Gil-G9 is connected to one of the terminals GTtl-GT9 which is individually identified with one of the trunk groups on link PLO. The numeric of each of the designations for these terminals corresponds to the trunk group with which the terminal is identified; for example, treminal GTO is identified with trunk group 0.

The cross-connection between the terminals GTO-GT9 of the position links PLQ-P19 and the terminals GTAO- GTAS of FIG. 4 is made in accordance with the class-ofservice assigned to each of the trunk groups on the links PLO-PL9. For instance, trunk group of link PLO has been assigned to a dial O class-of-service in this embodiment and, accordingly, terminals GT() and GTAO are cross-connected. There are ten terminals GTO-GT9 on each of the links PLO-PL9 and only six terminals GTA@- GTA9; therefore, certain of these GTA- terminals must be connected to more than one of the GT- terminals on each of the links PLO-PL9 since certain of the trunk groups on these links are assigned to serve the same classof-service calls.

Each of the terminals GTAO-GTA is also connected to an individual one of the cross-detector relays XG()- XGS over the leads GLU-GLS and contacts CWO-S through CWS-5. Each of these relays is a sensitive relay which operates if an electrical potential of suicient magnitude is present on the associated GL- lead. To illustrate, let it be assumed that a negative potential of sufficient magnitude is present on lead GLS as the result of a cross between leads GLO and GLS when the negative potential P3 is applied to lead GL() as later described. The presence of this potential on lead GLS immediately operates relay XGS over the path through contact CWS-S and the XGS relay winding to ground. Upon operating, relay XGS locks through its contact XG5-1 and the break contact of the alarm release key AR to the negative potential P4. The operation of relay XGS also closes its contact XGS-Z to activate the visual and audible alarm circuit ALM. Thereafter, an attendant may identify and correct the indicated cross and activate the key AR to open the locking path of relay XGS for releasing it.

By providing the XGO-XG5 cross-detector relay arrangement, the traffic regulator TR is enabled to insure that the control gate relays Gil-G9 of FIG. 4 are not falsely operated. In the event that the relays Gti-G9 were operated by foreign potentials applied to leads GL- as the result of falsely crossed leads, the regulation of call traffic would be seriously impaired. For example, if the relay G0 were falsely operated by a permanent negative potential on lead GLO and the XGO relay were not provided, nom-priority requests of dial O trunk circuits on link PLI) would be improperly blocked from being registered in the register-start circuit NPRSO. In addition, non-priority requests of dial O trunk circuits on the other links PL1-PL9 perhaps would be denied registration in t-he corresponding register-start circuits of those links since the negative potential on lead GLO would also operate the corresponding control gate relays G- of those links.

The control gate relays G0-G9 of FIG. 4 each comprise five break contacts each of which is individually connected in series with one of the register-start circuits NPRS- and a non-priority start lead NPS- of a trunk Icircuit in the same class-of-service trunk group. In gate lCG() of FIG. 1, for example, the break contacts Gil-1 through GO-S are serially connected between the NPS()- NPS4 leads and the register-start circuits NPRSO. When .a G- relay is operated iby a CW- relay, as later explained, .it opens its live break contacts to close the gate and thereby block non-priority request signals from being applied to the associated register-start circuit NPRS-.

Returning now to the previous description concerned with the circuit actions that follow the operation of relay CWO, it may be seen in FIG. 4 that operated relay CWO applies the potential P3 through contact CWO-6 to the lead GLO for operating all control gate relays, such as relay G0, associated with dial O class-of-service trunk groups. The operation of these relays blocks the registration of non-priority requests in the dial O registerstart circuits, such as circuit NPRSO of FIG. 1, of links PLO-PL9 until after trunk circuit TC00 of FIG. 1 has been connected to one of the operator positions OP1- OP66. Relay G0 of link PL!) operates over the path from ground through the G0 relay winding and terminals GTG and GTA@ to the potential on lead GLO. In operating, relay Gil opens its contacts G0-1 through G0-5 of FIG. 1 to block the application of non-priority requests of the trunk circuits T C01-TC04 (not shown) from the register-start circuit NPRSt) until after trunk circuit TCO() has been connected to one of the positions OP1- 0F66.

In the instant case, it has been assumed that an operator position is available to serve a dial O class-of-call. Accordingly, the traffic regulator TR will have signaled the link PLI) in a `manner as described later, that a position is avail-able. Link PL() then associates itself with one of the link controllers LCO-LC2 of FIGS. l and 2 and that controller proceeds to control the interconnection of trunk circuit TCG() and an available one of the positions OPI- OP66 via the switching network SN of FIG. 2, one of the position loops Lil-LN7 and position units PU1-PU66 in a manner as set forth in the Curtis disclosure.

After trunk circuit TCO() has been connected to a position, and if there is no other dial O trunk circuit on links PLO-PLQ which registered a non-priority request concurrently with circuit TCGO, the relay STO or STOP (not shown) opens contact STO-1 or STOP-1 of FIG. 3 to effect the release of relay CWO. In releasing, relay CWO opens its contact CWtlto release relay G0 on link PLO and all other corresponding G- relays associated with the dial O trunk groups on the links PLO-PL9. This will permit new non-priority requests from dial O trunk circuits on these position links to be registered in the appropriate register-start circuit NPRS-.

Thereafter, all of the CW-Z through CWS-2 contacts in the operate path of relay MGT in FIG. 3 are normal to indicate that all calls with the master -gate have been served. Thus, relay MGT may be reoperated by relay OG of FIG. 3 when the latter relay is operated as the result of the grounding of any one of the leads CWLO- CWLS as previously explained.

CAMA call-wailing and gate control-Referring t0 FIG. 7, a CAMA call-waiting relay CCW is provided in the traiiic regulator TR for controlling the gate relays GTO-GT3 in the CAMA position link CPL and thereby the regulation of the order in which the senders SOO-S39 of FIG. l are connected to the operator positions OPI- OP66. When a request has been registered in one of the register start circuits RSU-RSS in the CAMA position link CPL of FIG. 1, it results in the grounding of the lead CCWL of FIG. 8 under the control of the contacts STO-1 throng-h STS-1 of the group start relays STO-ST3 (not shown) of link CPL.

The ground on lead CCWL is extended through contact CCW-1, diode CD, lead CCWLA into FIG. 3 and the OG relay winding to potential P1 for operating relay OG. In operating, relay OG operates relay CW over the previously stated path. When all of the CWO-CWS relays are released and relays OG and CW are operated, relay MGT is operated over the path from potential P1 through its winding and the contacts CWS-2 through CWO-2, CW-l and OG-2 to ground.

Upon operating, relay MGT causes the operation of relay CCW over the path from the negative potential P5 through its winding and contact MGT-4 to the yground on lead CCWL. When operated, relay CCW locks via contact CCW-2 to the ground on lead CCWL. At the same time, relay CCW opens contact CCW-1 to effect the release of relay OG. Relay OG then opens Contact OG-Z to release relay MGT. Operated relay CCW also closes contact CCW-3 to lock relay CW operated.

The operation of relay CCW operates all of the gate relays GT 0-GT3 on the CAMA position link CPL over the path from ground through the GTO-GT3 relay windings in parallel, lead CCG and contact CCW-3 to the negative potential P6. In operating, the relay GTll-GTS open their respective break contacts, such as contacts GTi-ll through GTG-9 of FIG. l, wh-ich are serially connected with the leads SSG-S839 and the register-start circuits RSG-RSS t block the registration of new sen-der requests for connections to the positions OPI-0F66 until each of the senders having a registered request in the circuits RS-RSS has been connected to an operator position. After the last such sender has been connected to a position in a rnanner as described in the cited Breed et a-l. patent, the ground on lead CCWL is removed and relay CCW releases for enabling new sender requests for connections to an operator position to be registered in the circuits RSU-R83.

In FIG. 7, a sensitive cross-detector relay XCG is connected through contact CCW-4 to lead CCG for detecting foreign potentials on lead CCG and preventing such a potential from operating the gate relays GTG-GT3 and thereby causing the blocking of the registration of sender requests from the register-start circuits RSll-RS3 of FIG. l. Such a potential usually is connected to lead CCG as the result of a lead being falsely crossed with lead CCG and, if it is of a sufcient magnitude, it causes the operation of relay XCG. In operating, relay XCG closes contact XCG-I to notify the alarm circuit ALM of FIG. 4 of the cross. Operated relay XCG also closes a locking path for itself through contact XCG-2 and a break contact of the alarm release key ARI to the negative potential P6. Relay XCG thereafter is released after an attendant eliminates the cross condition and momentarily operates the alarm release key ARI to open the locking path for relay XCG.

Position availability signals t0 position links PLO- PL9.-The traic regulator TR maintains a constant check on all of the 66 operator positions OPI-0F65 of FIGS. l and 2 to ascertain if they are currently available to serve the six different class-of-service calls receivable by the trunk circuits associated with the position links PLQ-P159; This checking operation enables the regulator TR to send position available signals to all ten links PL0-PL9` and thereby allows each of those links to seize one of the three link controllers LCd-LCZ of F-IG. l only if an operator is available to serve a received call.

In FIG. 8, it may be seen that the regulator TR includes six relays PCAtl-PCAS for checking the availability of the 66 operator positions for serving the six different class-of-service calls. Each of these relays is identified with an individual one of the six class-of-service trunk groups provided on each of the links PLQ-PI. A PCA- relay is operated under the control of a trunk class relay TC-- (not shown in the present drawing but shown in FIG. 158 of the Curtis disclosure) in the key control position control circuit KCP of FIG. 8 when at least one of the positions OPI-0F66 of FIGS. l and 2 is available to serve calls of the particular class-of-service with which that PCA- relay is identilied.

Circuit KCP continually receives information concerning the availability of the positions OPI-0F66 from the position control circuits of the position units PUl-PU66 of FIGS. l and 2 as set forth in the Curtis disclosure. Thereafter, circuit KCP enables its trunk class relays TC- (not shown) to apply ground to the appropriate ones of the leads PCLtli-PCLS of FIG. 8. The presence of ground on a PCL- lead signifies that an operator is available and the absence thereof signifies that an operator is not available. Ground on a PCL- lead causes the operation of the associated PCA- relay over the obvious path. For example, the PCA@ relay FIG. 8 is operated over the Path from the ground on lead PCL through the PCA@ relay winding to potential P7 in this illustrative embodiment only if at least one of the positions OPI-@Peo is available to serve dial O calls.

The relays PCAll-PCAS are used to control the opertion of the six positions busy relays RPBll-RPBS in the trafc regulator TR, of which only the relays RPBtB and RPBS are shown in FIG. 4. Each of these RPBtl-RPBS I8 relays is operable under the control of one of the PCAtl- PCAS relays for supplying the positions busy and position available signals to each of the position links P Ltl- PL9 over the leads PBLll-PBLS of FIGS. 5 and 6. An RPB- relay is unoperated, or released', under control of a PCA- relay when at least one of the positions OP1-OP66 is available to serve a class-of-call identified Withlthat PCA- relay. In contradistinction, an RPB- relay is operated under the control of a PCA- relay when none of the positions OPl-OP66 is available to serve calls of the particular class-of-service with which that PCA- relay is identied. For example, relay RPB() is operated when relay PCA@ is unoperated and it operates over the path from the negative potential P20 through the lower winding of relay RPBO and contacts ACA-l and PCAll-I to ground. Upon operating, an RPB- relay may shunt its upper winding to ground through one of its own make contacts and break contacts of the associated call-waiting relay CW- and the ten priority frame relays PFtl-PF9 for making that relay RPB- a slow-releasing device. This slow-releasing characteristic is used, as hereinafter cxplained, for regulating the ordered sequence in which the positions OPI-0F66 are made available for serving the different classes-of-calls during heavy trafc periods.

It may `be noted that the operate path for each of the relays RPBtl-RPBS includes the break contact ACA-l of the all classes available relay ACA of FIG. 7. This relay is operated under control of the key control position control circuit KCP when at least one of the positions OPI-OPM is available to serve all classes-of-calls. Relay ACA is operated over the path from the negative potential P7 through its winding, `lead ACL to ground v-ia contact RTG-l in circuit KCP. The latter contact is controlled by relay RTG (which is not shown in the present drawing but is shown in FIG. 158 of the Curtis disclosure). Upon operating, relay ACA opens the operate paths for all of the relays RPBG-RPBS to signify that at `least one operator is available to servey all classes-of-calls.

Considering now the left-sides of FIGS. 5 and 6, each of the position links PLO-PL9 includes six position busy relays `PBtl-PBS for indicating the availability of the positions OPI-0F66 to serve the six different class-of-service calls. These relays also allow each position link to seize one of the link controllers LCO-LCZ of FIG. l, as set forth in the Curtis disclosure, only if an operator is available to serve `a service requesting trunk circuit associated with that link. The PB- relays 'of each of the links PLtl-PL9 are connected to an individual one of the ten sets of the leads PBLll-PBLS, of which only four sets are shown in FIGS. 5 and 6. Each ofthe PB- relays is operated to indicate that none of t-he positions OPI-0F66 is available to serve the class-of-c-all with which it is associated. The operate path for each PB- relay is from ground through its winding and a break contact of an LCC relay (not shown in the present drawing but shown in FIG. 106A of the Curtis disclosure) to the negative potential connected to the associated PBL- lead under control of either an RPB- relay or an NP- relay :as hereinafter explained. Upon operating, the PB- relay closes a locking path for itself to the negative potential on the PBL- lead through its make contact which bridges the LCC relay contact in its operate path. The PB- relay is released by the disconnection of the negative potential from the associated PBL- lead when one of the positions OPI-0F65 becomes available to serve the class-of-call with which it is associated.

In order to understand clearly the circumstances under which the negative potentials, or positions busy signals, are connected to the PBLtl-PBLS leads, it is advisable rst to describe the features of the NPG-NP9 relay circuit of FIG. 9 and the manner in which these relays are operated to apply positions busy signals over the ten sets of PLCli-PLCS leads of FIGS. 5 and 6 to the position links PLtl-PL9 when priority service requests Vare registered in these links. As previously stated, the

NPO-PN9 relays :are operated under control of the PFO-PF9 relays of FIG. 3, each of which is individually associated with one of the links PLO-PL9. When one of the PFO-PF9 relays is operated to signify that a priority request has been registered on the associated one of the links PLO-PL9, it opens the operate path for the correspondingly numbered one of the NPO-NP9 relays and, lat the same time, completes the operate circuits for all of the other ones of the NPO-NP9 relays.

For example, when relay PFO is operated, it opens its contact PFO-l of FIG. 9 in the operate path for relay NPO to prevent relay NPO from operatnig. Operated relay PFO also causes the operation of relays NPI-NP9. Relays NP1-NP4 operate over the paths from ground through the NPI-N4 relay windings in parallel, the associated 'break contacts of the relays PF1-PF4 and contact PFO-Z to the negative potential P9. Similarly, the relays NPS-NP9 operate over the paths from ground through the NPS-NP9 relay windings in parallel, the

associated break contacts of relays PF5-PF9 and contact PPO-3 to the negative potential P10.

It may be noted that if more than one of t-he FFO-P129 relays operate, the correspondingly numbered ones of the NPO-NP9 relays will be released and all of the other ones of the NPO-NP9 relays will be operated over the described paths. For example, when relays PFO and PF 9 are operated, the operate paths for the relays NPO and NP9 are opened at contacts PPO-1 and PF9-1 while the other relays NPI-NPS are operated over the previously traced paths.

Each of the NPO-NP9 relays is associated with an individual one of the position links PLO-PL9 and, when operated, applies positions busy signals to the busy leads PBLO-PBLS extending to that link. For the purpose -of illustration, let it be assumed that a priority request has been regis-tered in link PLO and, accordingly, has effected the operation of relays PFO and NPI-NP9, as well as, blocking of the operation of relay NPO as explained previously. Under these conditions, it may be seen in FIG. 5 that the negative potential P11 is connected to the links PL2, PL4, PL6 and PLS via the associated sets of leads PBLO-PBLS and the make contacts of the associated relays NP2, NP4, NP6 and NPS. Similarly, in FIG. 6, the negative potential P12 is connected to t-he links PL1, PLS, PLS, PL7 and PL9 via the associated leads PBLO-PBLS via the make co-ntacts of relays NP1, NPS, NPS, NP7 and NP9. Accordingly, the application of the potentials P11 and P12 to the leads PBLO-PBLS under control of the NPO-NP9 relays and in response to a priority request from -a trunk circuit, i

`the trunk circuits on link PLO causes the traic regulator f to alter the position available signals (ground on leads PBLO-PBLS) to position busy signals (negative potentials P11 and P12 on leads PBLO-PBLS) whereby the priority requesting circuit on link PLO is connected to an available operator position before any nonpriority requesting circuit.

The application ofthe negative potentials P11 and P12 to the PBLO-PBLS leads causes all positions busy relays PBO-PBS on each of t-he links PL1-PL9 to operate if that link is not presently connected to yone of the link controllers LCO-LC2. If one of the links PL1-PL9 is connected to a controller, the LCC- contacts in the operate pat-hs of `the PBO-PBS relays of that link are opened as described in the Curtis disclosure to prevent these relays from operating and interfering with the connection of a trunk circuit associated with that link. It is noted that only the PBO-PBS relays on link PLO are operated, as already explained, in accordance with the actual availability of the positions OP1-OP66 to serve the different classes-of-calls. This mode Iof signaling in- 20 sures that priority requesting trunk circuits are connected to the positions CP1-0F66 before any non-priority requesting trunk circuit, as set forth in the Curtis disclosure.

Each of the leads PBLO-PBLS of FIGS. 5 and 6 is connected to one of the six cross-detector relays XPBO-XPBS of FIG. 9 through a break contact of each one of the -ten non-priority relays NPO-NP9 and a break contact of one of the six position busy relays RPBO-RPBS. Each of these relays is a sensitive relay which operates if an electrical potential of sutlicient magnitude is present on the associated PBL- lead and causes audible and visual alarm signals to be provided for the maintenance personel. To illustrate, let it be assumed that the negative potential P11 is present on the lead PBL1 associated with position link PLO as a result of a cross between the leads PBL1 and PBLO when potential P11 is applied to lead PBLO via contacts RPB-Z and NPO-1 as later described. The presence of potential P11 on lead PBL1 immediately operates relay XPB1 over the path from ground through its winding and the contacts RPBl-l and NPO-2 to the negative potential on lead PBL1. Upon operating, relay XPB1 locks through its contact XPB1-1 and the break contact of the alarm release key AR2 to the negative potenial P13 of FIG. 9. The operation of relay XPB1 also closes its contact XPB1-2 to activate the visual and audible alarm circuit ALM of FIG. 3. Thereafter, an attendant may identify and correct the indicated cross and activate the key AR2 to open the locking path of relay XPB1 for releasing it.

By providing the XPBO-XPB5 cross-detector relay arrangement, the traic regulator TR is enabled to insure that position busy relays PBO-PBS of the position links PLO-PL9 are not falsely operated. In the event that any of the PB- relays was operated by a foreign potential on the associated lead PBL- as the result of crossed leads, all calls of the class-of-service associated with that particular PB- relay would be blocked from connection to the positions OP1-OP66 as long as the crossed lead condition persisted.

All operator positions busy.--The 66 operator positions OPI-O66 are divided into seven groups classied as the position .groups A-G in the Curtis system. This classification is to facilitate controlling the interconnection of the calling trunk circuits with operator positions and to insure that during certain traflic periods the seating of operators can be administered to avoid cases where the occupied positions are all in the same position group.

Each of the seven position groups is assigned to an individual one of the group busy relays GBA-GBG in the traic regulator of FIG. 8. A group busy relay GB- is operated under control of the position control circuits associated with the same group when the positions constituting that group are all busy, unoccupied, or otherwise not available for serving calls. For example, when all positions of group A are busy, the GBA relay is operated over the path from ground through its lower winding, contact PR-1, lead GBLO, and the break contact of the CAMA call-waiting relay CCW (not shown in the present drawing but shown in FIG. 2 of the J. Baumfalk et al. disclosure) to the negative potential P14 in the position control circuits, such as circuit PCC1 of FIG. l, of position group A.

Upon the operation of a GB- relay, the corresponding one of the group busy relays AGBA-AGBG of FIG. 7 is operated to inform the CAMA position link CPL that positions in the associated position group are unavailable for serving CAMA calls. For instance, upon the operation of relay GBA, the relay AGBA is operated over the path from ground through the AGBA relay winding, the cross-connection field, lead GBLA, and contact GBA-1 to the negative potential P15.

It may be seen in FIG. 7 that the cross-detector relays XGBA-XGBG as connected to the group busy leads GBLA-GBLG via the contacts GBA-2 through GBG-Z for detecting foreign potentials on these leads. Such assises potentials may be connected to these leads when they are crossed and a potential of sufficient magnitude is connected to one of these leads. For example, when leads GELA and GBLG are falsely crossed and the negative potential P15 is connected to lead GELA through contact GBA-ll, relay XGBG is operated over the path from ground through its winding and Contact GBC-2l to potential P15. In operating, relay XGBG locks through its contact XGBG-I and the break contact of the alarm release key ARS to potential P5. Operated relay XGBG also closes its contact XGBG-l to activate the alarm cir cuit ALM of FIG. 4 for informing the maintenance personnel of the cross condition. After the cross condition has been corrected, an attendant may .activate the key ARB for releasing relay XGBG and thereby deactivating the alarm circuit ALM. This cross detector circuitry prevents the AGBA-AGBG relays from being falsely operated and insures that correct information is given to the CAMA link CPL concerning the availability of the positions OPI-F65.

When one of the group busy relays GBA-CBG of FIG. 8 operated, as explained, it may shunt its other winding to ground through one of its make contacts and a make contact of one of the CW-CWS relays of FIG. 3 for making itself slow-releasing. This slow-releasing characteristic is used to regulate the ordered sequence in which an operator position becomes available for serving the special service and the CAMA calls during heavy traffic conditions. Each of the relays GBA-GBC is released when an operator position in the corresponding group becomes Aagain available to serve calls and the negative potential is disconnected from the lead GBL()- GBL7.

Turning now to the feature whereby the traic regulator TR regulates the ordered sequence in which the positions OPI-0F66 are made available for serving special service and CAMA calls, it will be initially assumed that all positions OPI-0F66 in the position groups A-G are busy and that the positions become available, or idle, one-by-one. Let it further be assumed that a position becomes available in group A for serving dial O calls and that a trunk circuit associated with one of the position links PLti-PL9 has already activated the CW@ relay of FIG. 3 as previously explained. Under these conditions, the position busy relays RPBtB-RPBS of regulator TR and PB-PBS of all links PLQ-P13 will be operated. It may be noted that the upper winding of the relay RFB@ of FIG. 3 is not shunted to ground at this time because contact CW9 is opened, and, accordingly, relay RPBtl is a relatively fast-releasing device. In contradistinction, the upper windings of all of the operated relays GBA-GBG will be shunted to ground, as described previously, for making these relays slowreleasing devices with respect to relay RPBtl.

When the operator position in group A becomes available under the foregoing conditions, the Lrac regulator TR will make that position available for connection to a dial O trunk circuit having a registered request in one of the links PLQ-PLQ before it is availaible to a CAMA trunk circuit which is also requesting connections to an operator position. The regulator TR regulates the order in which the position is made so available `by the controlled release times of the relays RFB@ and GBA. At the time that the position becomes idle, the associated position control circuit signals the key control position control circuit KCP of FIG. 8 to release relay PCAt). In releasing, relay PCAt) quickly releases relay RFB@ which, in turn, signals the position links PLO-PL9, as previously described, that a position is available to serve a dial O call. A preferred one of the links PL-PL9 thereafter seizes one of the controllers LCtl-LCZ of FIG. l for effecting the interconnection of the idle position with a dial O trunk circuit having a service request registered in that link. A short time after relay RFB@ has released and the preferred one of t-he links PLtl-PL9 'has seized the controller, the relay GBA releases and informs the CAMA position link CPL that a position is available. However, the time delay between the release actions of relays RPBt) and GBA insures that one of the controllers LC-LCZ of FIG. l will seize the available position before the CAMA link controller CLC of FIG. 1.

After all of the trunk circuits, which have registered requests in the position links PLO-PLS? and activated the associated one of the CWt-CW relays of FIG. 3, have been connected to an operator position during the heavy trafc period, the CWtD-CWS relays are released. In addition, if the operator positions are yet all busy and there are no priority requests registered in the links PLE)- PL9, the upper windings of t-he RPBG-RPBS relays are then shunted to ground, as previously explained, for making them slow-releasing devices. Furthermore, the released relays CWO-CW5 open the shunt path about the secondary windings of the GBA-CBG relays for making these relays faster releasing than the RPBtl-RPBS relays are at present. Accordingly, when the next operator position becomes idle, the associaed B- relay is released before -any of the RPBtLRPBS relays. This release sequence enables the CAMA position link CPL to seize the CAMA controller CLC for effecting the interconnection of a CAMA trunk circuit with the available position before any of the position links PLtl-PL9 is enabled to'seize one of the controllers LCO-LC2 in response to the receipt of a service request from an associated trunk circuit.

i. When all of the positions OPI-0F66 are busy, the CAMA lamp CL of FIG. 8 at each of the positions may be lighted to notify the operators that CAMA calls are awaiting service. Each CL lamp is energized over the path in FIG. 8 from ground through the lamp, lead CLL, Contact GBG, GBB- through GBF- (not shown), GBA-5 and CCW-6 to potential P16. As a result, if one ofthe operators is busy serving a long work-time call and she ascertains that the completion of that call will be delayed, she has the option of causing a short worktime CAMA call to be connected over a CAMA loop to her position for immediate service on a so-called overlap basis. In serving the calls on an overlap basis, the delayed call circuit is temporarily disconnected from the operators telephone facilities while these facilities are connected to a CAMA call circuit. After the CAMA call has tbeen served, the operator telephone facilities are automatically disconnected from the CAMA call circuit and reconnected to the delayed call circuit.

The manner in which CAMA calls are served on an overlap basis is set forth in detail in the cited I. Baumfalk et al. disclosure. As set forth therein, the operator initiates the connection of a CAMA call to her position on an overlap basis by depressing a CAMA call-waiting key CAMA-CW (not shown) which results in the operation of a CCW relay (not shown) in the associated position control circuit. When the latter relay operates, it temporarily disconnects the negative potential P14 from the associated one of the GBLtB-GBL leads for releasing the associated one of the GBA-GBG relays in the traffic regulator TR which, in turn, causes the corresponding one of the AGBA-AGBG relays on the CAMA link CPL to be released for causing a CAMA call to be connected to the requesting operators position for service as set forth in the cited Baumfalk et al. disclosure. While the foregoing operations are in progress, the RPBO-RPBS relays of FIG. 4 remain operated to block the connection of service requesting trunk circuits of links PLO-P149 to the positions OPI-0F66. After the CAMA call has been served by the operator, the delayed call is automatically reconnected to the operator telephone facilities for service.

Proceeding now to another aspect of the traffic regulator TR, a description is presented of the manner in which it regulates the ordered sequence in which the operator positions are made available for serving calls on trunk circuits in the different class-of-service trunk groups 

1. IN COMBINATION, A PLURALITY OF OPERATOR POSITIONS FOR SERVING TELEPHONE CALLS, GROUPS OF CALLING CIRCUITS, EACH OF SAID CALLING CIRCUITS HAVING MEANS FOR SELECTIVELY REQUESTING NON-PRIORITY AND PRIORITY CONNECTIONS TO SAID POSITIONS, A PLURALITY OF POSITION CONNECTORS EACH BEING INDIVIDUALLY CONNECTED TO A PREDETERMINED NUMBER OF SAID GROUPS OF CIRCUITS AND BEING RESPONSIVE TO THE RECEIPT OF NON-PRIORITY AND PRIORITY REQUESTS FROM SAID CIRCUITS FOR CONNECTING SAID REQUESTING CIRCUITS TO THE AVAILABLE ONES OF SAID POSITIONS, MEANS FOR SUPPLYING SIGNALS TO SAID CONNECTORS TO SIGNIFY THE ACTUAL AVAILABILITY OF SAID POSITIONS TO SERVE SAID CALLS, AND MEANS RESPONSIVE TO A PRIORITY REQUEST FROM ANY ONE OF SAID CIRCUITS FOR SELECTIVELY ALTERING SAID SIGNALS TO EFFECT THE CONNECTION OF SAID ONE CIRCUIT THROUGH SAID CONNECTED CONNECTOR TO AN AVAILABLE ONE OF SAID POSITIONS ON A PRIORITY BASIS WITH RESPECT TO SAID CIRCUITS REQUESTING NON-PRIORITY CONNECTIONS. 